Bus bar module

ABSTRACT

A bus bar module includes a circuit body, a bus bar, a holder, and a cover configured to be assembled to the holder to protect the circuit body and the holder. The circuit body includes a belt-like main line that extends in a first direction, a belt-like branch line that extends from the main line so as to branch from the main line, and a connection portion provided in a position closer to a distal end of the branch line than a folded portion the branch line. The cover is structured so as to be stretchable and shrinkable in the first direction in accordance with a stretching and a shrinking of the holder in the first direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application (No.2018-130912) filed on Jul. 10, 2018 and Japanese Patent Application (No.2018-144238) filed on Jul. 31, 2018 and, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a bus bar module.

2. Description of the Related Art

Conventionally, a bus bar module has been used in such a manner as to beassembled to a battery assembly (a battery module where a plurality ofbattery cells are disposed so as to be assembled) as a driving powersource mounted on, for example, an electric car and a hybrid car (forexample, see JP-A-2014-220128).

A bus bar module described in JP-A-2014-220128 is provided with: aplurality of bus bars connecting between the positive electrodes and thenegative electrodes of the battery cells assembled so as to adjoin eachother; and a voltage detection line connected to the bus bars in orderto monitor the battery cells. This voltage detection line is formed bybundling a plurality of electric wires of a typical structure where acore wire is covered with an insulating film.

Typically, the battery cells constituting a battery assembly stretch andshrink in the assembled direction due to the operation heat accompanyingcharge and discharge, the temperature of the external environment andthe like. As a consequence, the battery assembly (battery module) alsobecomes deformed so as to stretch and shrink in the assembled directionof the battery cells. Moreover, typically, the size of the batteryassembly in the assembled direction can differ among the manufacturedbattery assemblies (manufacturing variations can occur) due to theassembly tolerances when a plurality of battery cells are disposed so asto be assembled. Accordingly, in order to conform to the deformation ofthe battery assembly and the manufacturing variations, the bus barmodules is typically designed so that the length of the voltagedetection line has a certain extent of margin.

However, in the above-described conventional bus bar module, when thenumber of laminations of the battery cells is increased, for example,for the purpose of increasing the capacity of the battery assembly, thenumber of electric wires constituting the voltage detection line alsoincreases. As a consequence, if the voltage detection line is formed bybundling the multiplicity of electric wires, the overall stiffness ofthe voltage detection line (accordingly, the stiffness of the bus barmodule) increases, so that it can be difficult to improve theworkability (assemblability) at the time of assembly of the bus barmodule to the battery assembly. For the same reason, it can be difficultfor the bus bar module to stretch and shrink so as to be sufficientlyconform to the deformation and the manufacturing variations of thebattery assembly.

SUMMARY OF THE INVENTION

The present invention is made in view of the above-describedcircumstances, and an object thereof is to provide a bus bar moduleexcellent in the assemblability to the battery assembly and theconformability to the deformation and the manufacturing variations ofthe battery assembly.

To attain the above-mentioned object, a bus bar module according to thepresent invention is characterized by the following [1] to [3]:

[1] A bus bar module configured to be attached to a battery assemblyhaving a plurality of single cells which are assembled to each otheralong a first direction, the bus bar module including:

a circuit body configured by a flexible board on which a wiring patternis provided;

a bus bar configured to be connected to an electrode of each of thesingle cells;

a holder configured to hold the bus bar and being stretchable andshrinkable in the first direction; and

a cover configured to be assembled to the holder to protect the circuitbody and the holder,

in which the circuit body includes:

-   -   a belt-like main line that extends in the first direction;    -   a belt-like branch line that extends from the main line so as to        branch from the main line, a part of the branch line extending        in the first direction and including a folded portion having a        shape folded back around an axis intersecting with the first        direction; and    -   a connection portion provided in a position closer to a distal        end of the branch line than the folded portion and configured to        be connected to the bus bar; and

in which the cover is structured so as to be stretchable and shrinkablein the first direction in accordance with a stretching and a shrinkingof the holder in the first direction.

[2] In the bus bar module according to the above [1], the cover has aplurality of portions arranged in the first direction and the pluralityof portions are coupled to each other so as to be movable relatively toeach other.[3] In the bus bar module according to the above [2], a movable range ofeach of the plurality of portions is limited, and each of the pluralityof portions is structured so as to prevent an inside and outside of thecover from communicating with each other even when each of the pluralityof portions is arranged in the movable range.

According to the bus bar module of the structure of the above [1], thecircuit body formed of a flexible board is formed of the belt-like mainline and the belt-like branch line branching from the main line. Atleast part of the branch line includes the folded portion having theshape folded back around the axis intersecting with the assembleddirection of the single cells. For this reason, when the batteryassembly stretches or shrinks in the assembled direction due to thermaldeformation of the single cells, the folded portion of the branch lineof the circuit body bends and stretches, whereby the bus bars aremovable in the assembled direction of the single cells. Likewise, by thefolded portion of the branch line of the circuit body bending andstretching, variations in the size of the battery assembly in theassembled direction due to the assembly tolerances of the single cellscan be absorbed. In other words, the bus bar module of the presentstructure is capable of easily handling the stretch and shrinkage andthe manufacturing variations of the battery assembly substantially bythe deformation of only the branch line without the need for anydeformation of the main line of the circuit body. Moreover, even when amultiplicity of circuit structures are contained, the flexible board istypically easy to become deformed flexibly with a far smaller force thannormal electric wires used for the above-described conventional bus barmodule. For this reason, the assemblability to the battery assembly issignificantly improved.

Further, since the cover also stretches and shrinks in the laminationdirection as the holder stretches and shrinks in the laminationdirection, the circuit body and the bus bar can be protected from theoutside while the assemblability to the battery assembly and theconformability to the manufacturing variations are improved.

According to the bus bar module of the structure of the above [2], bycoupling a plurality of parts so as to be relatively movable in thelamination direction, a cover stretchable and shrinkable in thelamination direction in response to the stretch and shrink of the busbar in the lamination direction can be easily realized.

According to the bus bar module of the structure of the above [3], evenif the plurality of parts constituting the cover each move as the busbar stretches and shrinks, the inside and outside of the covert do notcommunication with each other. Consequently, even if the cover stretchesand shrinks, the condition where the circuit body and the bus bar areprotected from the outside can be maintained.

According to the present invention, a bus bar module can be providedthat is excellent in the assemblability to the battery assembly and theconformability to the deformation and the manufacturing variations ofthe battery assembly.

The present invention has been briefly described above. Further, detailsof the present invention will be further clarified by reading throughthe mode for carrying out the invention (hereinafter, referred to as“embodiment”) described below with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall perspective view of a bus bar module according tothe present embodiment.

FIG. 2 is a perspective view of a battery assembly to which the bus barmodule to which the present invention is applied is assembled.

FIG. 3 is a perspective view where an end portion of a circuit body isenlarged.

FIG. 4 is a perspective view showing the structure of a main line, firstbranch portions and second branch portions constituting the circuitbody.

FIG. 5A is a perspective view showing a condition where the secondbranch portion is bent in an S shape as a whole, FIG. 5B is aperspective view showing a shape into which the second branch portion isdeformed when the bus bar relatively moves rearward, and FIG. 5C is aperspective view of a condition where the bus bar relative moves forwardso that the second branch portion stretches.

FIG. 6 is a perspective view showing a part of the holder.

FIG. 7 is a perspective view of an accommodation space in a bus baraccommodating portion.

FIGS. 8A to 8C are perspective views showing modifications of a foldedportion of the second branch portion constituting the circuit body; FIG.8A shows a case where the folded portion is Z-shaped as a whole, FIG. 8Bshows a case where the folded portion is C-shaped as a whole, and FIG.8C shows a case where the folded portion is 0-shaped as a whole.

FIG. 9A is a perspective view showing a modification of the first branchportion, and FIG. 9B is a perspective view showing a modification of aposition of branch of the main line and the branch line.

FIG. 10 is a perspective view where the periphery of the position ofcontact between a connection piece of the bus bar and a connectionportion of the second branch portion is enlarged.

FIG. 11A is a top view of the periphery of the connection position shownin FIG. 10, and FIG. 11B is an A-A cross-sectional view of FIG. 11A.

FIG. 12A is a view, corresponding to FIG. 11A, of the bus bar moduleaccording to a modification of the present embodiment, FIG. 12B is aview, corresponding to FIG. 11A, of the bus bar module according toanother modification of the present embodiment, and FIG. 12C is a view,corresponding to FIG. 11A, of the bus bar module according to stillanother modification of the present embodiment.

FIG. 13A is a perspective view where the periphery of the position ofconnection between the connection piece of the bus bar and theconnection portion of the second branch portion on the bus bar moduleaccording to another modification of the present embodiment is enlarged,and FIG. 13B is a B-B cross-sectional view of FIG. 13A.

FIG. 14A is a cross-sectional view corresponding to an upper side metallayer on a part of the circuit body, and FIG. 14B is a cross-sectionalview corresponding to a lower side metal layer on part of the circuitbody.

FIG. 15 is a cross-sectional view where the periphery of one branchportion on the circuit body shown in FIG. 14A is enlarged.

FIG. 16A is a cross-sectional view corresponding to the upper side metallayer in the periphery of the front end portion of the circuit body, andFIG. 16B is a cross-sectional view corresponding to the lower side metallayer in the periphery of the front end portion of the circuit body.

FIG. 17 is a cross-sectional view corresponding to FIG. 16B at the frontend portion of the circuit body according to another modification of thepresent embodiment.

FIG. 18A is a perspective view showing a manner in which a cover isattached to the holder of the bus bar module, and FIG. 18B is aperspective view showing the condition where the cover is attached tothe holder of the bus bar module.

FIG. 19 is a side view for explaining the position of engagement betweenthe holder and the cover.

FIG. 20A is a perspective view of a cover in the assembled condition,and FIG. 20B is an exploded perspective view of the cover.

FIG. 21A is an upper view of the cover in the assembled condition, FIG.21B is a cross-sectional view corresponding to the C-C cross section ofFIG. 21A on the cover in the most stretched condition, and FIG. 21C is across-sectional view corresponding to the C-C cross section of FIG. 21Ain the most shrunken condition.

FIG. 22 is a perspective view showing the condition where a protectorattached to the circuit body exposed from the cover is fixed to thecover.

FIG. 23A is an upper view of the protector attached to the circuit bodyexposed from the cover, and FIG. 23B is a lower view of the protectorattached to the circuit body exposed from the cover.

FIG. 24A is a schematic view for explaining a manner in which aconnector provided on the front end portion of the circuit body movesforward under the condition where the protector is fixed to the cover,and FIG. 24B is a schematic view for explaining a manner in which theconnector provided on the front end portion of the circuit body movesrearward under the condition where the protector is fixed to the cover.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS Embodiment

Hereinafter, referring to the drawings, a bus bar module 10 according toan embodiment of the present invention will be described. The bus barmodule 10 according to the present embodiment is used in such a manneras to be assembled to a battery assembly (a battery module where aplurality of single cells are disposed so as to be assembled) as adriving power source mounted on, for example, an electric car and ahybrid car.

(Structure of the Battery Assembly)

First, a battery assembly 1 to which the bus bar module 10 of thepresent embodiment is attached will be described. As shown in FIG. 2,the battery assembly 1 is formed by linearly connecting a plurality ofsingle cells 2. The single cells 2 each have a positive electrode 4 anda negative electrode 5 provided so as to project on the top portion of abattery body (body) 3 formed in a rectangular shape. The positiveelectrode 4 and the negative electrode 5 are disposed away from eachother on an electrode surface 6 of the battery body 3, and are eachprovided so as to substantially vertically project upward from theelectrode surface 6 in a cylindrical shape.

In the battery assembly 1, the single cells 2 are arranged so as to beassembled in a predetermined direction (assembled direction) in such amanner that the positive electrodes 4 and the negative electrodes 5 ofthe adjoining single cells 2 alternate with each other. In this batteryassembly 1, for example, the positive electrode 4 of one of the singlecells 2 corresponding to both ends of the series-connected single cells2 is the total positive electrode, whereas the negative electrode 5 ofthe other of the single cells 2 is the total negative electrode.

(General Structure of the Bus Bar Module)

Next, the bus bar module of the present embodiment will be described. Asshown in FIG. 1, the bus bar module 10 has: a circuit body 20 formed ofa flexible board (FPC) and to which bus bars 25 (see FIG. 3) connectedto the positive electrodes 4 and the negative electrodes 5 of the singlecells 2 are attached; and a holder (wire routing member) 30 foraccommodating and holding the circuit body 20 and for the attachment tothe battery assembly 1.

As shown in FIGS. 1 and 3, the circuit body 20 has a belt-like main line21 disposed in the assembled direction on the single cells 2 and where aplurality of wiring patterns (details will be described later) areprovided. To an end portion of the main line 21, a connector 212 isattached through a voltage detection line 211 pulled out from the mainline 21. The connector 212 is connectable to a later-described voltagedetector 60 (see FIG. 22).

On the side portions of the main line 21 in the length direction (in thepresent example, substantially coinciding with the “assembled direction”of the battery assembly 1), belt-like first branch portions 22 extendingin a direction intersecting with the length direction and thicknessdirection of the main line 21 (outside of the main line 21 in the widthdirection) are provided, and at the leading end of each first branchportion 22, a belt-like second branch portion 23 extending in adirection parallel to the assembled direction of the battery bodies 3 isprovided. The main line 21, the first branch portions 22 and the secondbranch portions 23 are formed of an FPC. Therefore, the main line 21,the first branch portions 22 and the second branch portions 23 areflexibly deformable particularly in a direction orthogonal to thesurface of each.

As shown in FIGS. 4 and 5A, the second branch portions 23 each have afolded portion 231 folded back around axes L1 and L2 (in other words,around axes extending in the width direction of the second branchportion 23) intersecting with the assembled direction of the batteryassembly 1 (in the present example, substantially coinciding with theextension direction of the second branch portion 23). In the presentexample, the second branch portions 23 are each bent in an S shape(including an inverted S shape) as a whole by a first folded portion231A folded back with respect to the axis L1 and a second folded portion231B folded back with respect to the axis L2. For this reason, thesecond branch portion 23 is movable in the length direction of the mainline 21 (the assembled direction of the battery assembly 1) andstretchable and shrinkable also in the vertical direction.

The first branch portion 22 is provided so as to be flush with the mainline 21 outside the main line 21, and the second branch portion 23 isconnected to the first branch portion 22. For this reason, the secondbranch portion 23 is provided outside the main line 21 in the widthdirection, and is provided so as to be S-shaped downward under thecondition where the relative positions of the battery assembly 1 and thecircuit body 20 do not change (see FIG. 5A). For this reason, the busbar 25 is situated below the plane of the main line 21 outside the mainline 21 in the width direction.

Moreover, on the end portion of the second branch portion 23 opposite tothe first branch portion 22, a leading end portion 232 having a surfacesubstantially parallel to the main line 21 is provided, and to the uppersurface of the leading end portion 232, a connection portion 24 isattached. The lower surface of the connection portion 24 is providedparallel to the lower surface of the main line 21 in a different heightposition, and the lower surfaces are away from each other. The uppersurface of the connection portion 24 is connected to the bus bar 25connecting the positive electrode 4 and the negative electrode 5 of theadjoining single cells 2 in the battery assembly 1. Thereby, the secondbranch portion 23 is connected to the electrodes of each single cell 2through the connection portion 24 and the bus bar 25, so that thevoltage detection line 211 is connected to the electrodes.

As shown in FIGS. 3 and 5A to 5C, the bus bar 25 has: a bus bar body 251which is a plate-like member formed of a conductor (for example, made ofcopper) and is rectangular as a whole; and a connection piece 252projecting from the bus bar body 251 toward the main line 21. The busbar body 251 is provided with two electrode holes 253 through which thepositive electrode 4 and the negative electrode 5 of the adjoiningsingle cells 2 are passed. At the end portion on the side of the mainline 21 and the end portion on the opposite side on the bus bar body251, positioning concave portions 254 are provided so as to correspondto intervals between the two electrode holes 253. Moreover, to the lowersurface of the connection piece 252 of the bus bar body 251, theconnection portion 24 of the second branch portion 23 is connected. Aconcrete form of the connection between the connection piece 252 of thebus bar 25 and the connection portion 24 of the second branch portion 23will be described later.

A bus bar 25A provided on each end of the main line 21 in the lengthdirection is connected to the total positive electrode or the totalnegative electrode, and is provided with one electrode hole 253 throughwhich the total positive electrode or the total negative electrode ispassed. To the bus bar 25A, a power cable (not shown) that derives powerfrom the battery assembly 1 is connected. The internal structure of themain line 21, the first branch portions 22 and the second branchportions 23 constituting the circuit body 20 will be described later.

(Structure of the Holder)

As shown in FIG. 6, the holder 30 is formed of, for example, resin, andhas, in a central portion in the width direction, a main lineaccommodating portion 31 extending in the assembled direction of thesingle cells 2 and accommodating and holding the main line 21. The mainline accommodating portion 31 is provided with main line support members311 at predetermined intervals in the length direction of the main line21 that it accommodates, and the main line 21 is routed on the main linesupport members 311. When the main line 21, the first branch portions 22and the second branch portions 23 have a strength of a degree capable ofmaintaining a condition where the circuit body 20 of the present exampleis self-standing without the support by the main line support members311, it is unnecessary to provide the main line support members 311.However, even in this case, the main line support members 311 may beprovided in order to deliver an auxiliary support function when thecircuit body 20 cannot maintain the self-standing condition for somereason. As described above, the circuit body 20 may be configured so asto maintain the above-mentioned condition by using the main line supportmembers 311 or may be configured so as to be self-standing without theuse of the main line support members 311.

On each outer side of the main line accommodating portion 31 in thewidth direction, a bus bar accommodating portion 32 accommodating thebus bar 25 is provided. In the bus bar accommodating portion 32, aplurality of accommodation spaces 33 accommodating the bus bars 25 areprovided in the assembled direction of the single cells 2. As shown alsoin FIG. 7, the adjoining accommodating spaces 33 are separated bypartitions 34 to prevent contact between the adjoining bus bars 25. Oneach end portion of the main line 21 in the length direction, anaccommodation space 33A accommodating the bus bar 25A connected with thepower cable (not shown) is provided, and a power cable accommodatingportion 36 is provided continuously with the accommodation space 33A.

As shown in FIG. 7, the accommodation space 33 is a rectangular spacethat is open at the top and partitioned by an outer wall 331 on theoutside and an inner wall 332 on the inside in the width direction, anda pair of partitions 34 on both sides in the assembled direction. Oneside of each partition 34 in the assembled direction (left side in FIG.7) is connected to the outer wall 331 and the inner wall 332 through astretching and shrinking portion 35. Consequently, the accommodationspace 33 is stretchable and shrinkable in the assembled direction.

The lower end portion of the outer wall 331 and the lower end portion ofthe inner wall 332 are coupled by a coupling plate 333. On the lower endportion of the outer wall 331 and the lower end portion of the innerwall 332, engagement claws 334 are provided on both sides with thecoupling plate 333 in between. This enables the bus bar 25 to be heldbetween the coupling plate 333 and the engagement claws 334. Moreover,on the inner side surface of the outer wall 331 and the inner sidesurface of the inner wall 332, projections 338 are provided so as toproject inward in a central portion in the assembled direction. Theseprojections 338 are fitted in the positioning concave portions 254 ofthe bus bar 25 (see FIG. 5A) to position the bus bar 25.

The inner wall 332 is provided with a cut part 336, and incorrespondence with the cut part 336, a support plate 337 is provided soas to project inward. Thereby, the connection piece 252 of the bus bar25 accommodated in the accommodation space 33 is supported by thesupport plate 337.

Moreover, on each side of the coupling plate 333 in the couplingdirection, a space 335 is provided. Consequently, the positive electrode4 and the negative electrode 5 of the single cell 2 can be exposed tothe inside of the accommodation space 33 from the space 335, so thatthey can be connected to the electrode holes 253 of the bus bar 25accommodated in the accommodation space 33. Instead of the couplingplate 333, a bottom plate may be provided where cut parts or holescorresponding to the positive electrode 4 and the negative electrode 5of the single cell 2 are provided.

As shown in FIG. 1, the holder 30 accommodates and holds a part of thecircuit body 20 situated on the rear of a position a predeterminedlength behind the front end of the main line 21 to which the connector212 is attached (in other words, of the circuit body 20, a part within arange where at least the position of branch of the main line 21 and thefirst branch portion 22 is present). In other words, the part of apredetermined length from the front end of the main line 21 to which theconnector 212 is attached (hereinafter, referred to as “exposed part213”) is not accommodated in the holder 30 but exposed from the holder30.

(Operation of the Bus Bar Module)

Next, the operation of the bus bar module 10 will be described. FIG. 5Ashows a condition where the second branch line is bent in an S shape asa whole, FIG. 5B shows a condition where the second branch line slightlystretches rearward, and FIG. 5C shows a condition where the secondbranch line stretches forward.

As described above, the main line 21 is routed on the main line supportmembers 311 of the holder 30, and movable upward and in the lengthdirection. Moreover, the bus bar 25 is fixed to the inside of theaccommodation space 33 of the holder 30, and the accommodation space 33is movable in the length direction of the main line 21. The main line 21and the bus bar 25 are connected through the second branch portion 23bent in an S shape (see FIG. 5A).

Even if the relative positions of the battery assembly 1 and the circuitbody 20 are changed, for example, due to a deformation of the batteryassembly 1 under this condition and this changes the relative positionsof the main line 21 and the bus bars 25, the changes (shifts) of therelative positions can be absorbed by the bending and stretching of thesecond branch portions 23. Likewise, even if the size of the batteryassembly 1 in the assembled direction differs among the manufacturedbattery assemblies 1 due to the assembly tolerances of a plurality ofsingle cells 2, the manufacturing variations can be absorbed by thebending and stretching of the second branch portions 23.

More specifically, FIG. 5B shows a case where the bus bar 25 is slightlyshifted rearward (rightward in FIG. 5B) with respect to the main line21. In this case, the S shape of the folded portion 231 of the secondbranch portion 23 is deformed to thereby allow the shift of the bus bar25. Moreover, FIG. 5C shows a case where the bus bar 25 is largelyshifted forward (leftward in FIG. 5C) with respect to the main line 21.In this case, the S shape of the folded portion 231 of the second branchportion 23 stretches to allow the shift of the bus bar 25. Although notshown, when the main line 21 moves upward or downward to change theposition relative to the bus bar 25, the S shape of the folded portion231 stretches in the vertical direction to thereby allow the change ofthe relative position.

In the above-described embodiment, a case is described where the foldedportions 231 of the second branch portions 23 are bent in an S shape(including an inverted S shape) as a whole. In addition, as shown inFIG. 8A, the folded portions 231 may be folded in a Z shape (includingan inverted Z shape) as a whole. Moreover, as shown in FIG. 8B, thefolded portions 231 may be formed in a C shape (including an inverted Cshape) as a whole. Further, as shown in FIG. 8C, the folded portions 231may be formed in an O shape as a whole. As in the example shown in FIG.8C, the branch lines 22 and 23 may be configured so that the lowersurface of the main line 21 and the lower surfaces of the connectionportions 24 are flush with each other as required.

Moreover, for example, in the above-described embodiment, a case isdescribed where the first branch portions 22 extend on the same plane asthe main line 21; however, as shown in FIG. 9A, the first branchportions 22 may be provided in a direction intersecting with the lowersurface of the main line 21 (for example, a downward directionorthogonal to the main line 21 in FIG. 9A). Further, for example, in theabove-described embodiment, a case is described where the first branchportions 22 branch from side portions of the main line 21, as shown inFIG. 9B, an opening 29 may be provided in a central area different fromthe side portions of the main line 21 so that the first branch portions22 branch from the central area of the main line 21.

(Internal Structure of the Main Line and the Branch Lines Constitutingthe Circuit Body)

Next, referring to FIGS. 11B, 14A, 14B and 17, the internal structure ofthe main line 21, the first branch portions 22 and the second branchportions 23 constituting the circuit body 20 will be described.

As described above, the main line 21, the first branch portions 22 andthe second branch portions 23 constituting the circuit body 20 areformed of an FPC. As shown in FIG. 11B, (the FPC constituting) thecircuit body 20 is formed of a resin layer 201, and an upper side metallayer 203 a and a lower side metal layer 203 b so as to be sandwiched inthe resin layer 201. Typically, the resin layer 201 is made ofpolyimide, and the upper side metal layer 203 a and the lower side metallayer 203 b are made of copper (Cu). As described later, in the presentembodiment, a conventionally required reinforcing plate for suppressingcurving and the like of the circuit body 20 can be omitted by supportingthe circuit body 20 with the bus bars 25. In actuality, the circuit body20 is provided with an adhesive layer (not shown) that tightly fixesthese layers together. However, for convenience of explanation, theillustration of the adhesive layer is omitted in FIG. 11B.

The upper side metal layer 203 a situated on the upper side (obverseside) of the center of the resin layer 201 in the thickness directionand the lower side metal layer 203 b situated on the lower side (reverseside) of the center of the resin layer 201 in the thickness directionare embedded inside the resin layer 201. The upper side metal layer 203a and the lower side metal layer 203 b are separated from each other inthe thickness direction of the resin layer 201, and the resin layer 201is interposed therebetween. That is, the upper side metal layer 203 aand the lower side metal layer 203 b are insulated from each other.

As shown in FIGS. 14A and 16A, the upper side metal layer 203 a formsupper side wiring patterns 204 a as part of the above-mentionedplurality of wiring patterns, upper side dummy patterns 205 aindependent of the upper side wiring patterns 204 a and theabove-described connection portions 24 independent of the upper sidewiring patterns 204 a.

As shown in FIGS. 14B and 16B, the lower side metal layer 203 b formslower side wiring patterns 204 b as the remaining part of theabove-mentioned plurality of wiring patterns and lower side dummypatterns 205 b independent of the lower side wiring patterns 204 b. Thecorresponding upper side wiring patterns 204 a and lower side wiringpatterns 204 b are interconnected so as to be electrically continuouswith each other in the thickness direction of the circuit body 20through corresponding via holes 206 (see FIGS. 14A, 14B, 16A and 16B).

As shown in FIGS. 14A, 14B, 16A and 16B, regarding the first and secondbranch portions 22 and 23, on one side in the width direction (the rightside in FIGS. 14A and 14B), of the plurality of first branch portions 22and second branch portions 23 provided on both sides of the main line 21in the width direction, the corresponding upper side wiring patterns 204a continuously extend from the neighborhood of the tail end portions ofthe second branch portions 23 by way of the first and second branchportions 22 and 23 and the main line 21 over to the connector 212connected to the front end portion of the circuit body 20, whereby thefirst and second branch portions 22 and 23 and the connector 212 areconnected so as to be electrically continuous.

On the other hand, regarding the first and second branch portions 22 and23, on the other side in the width direction (the left side in FIGS. 14Aand 14B), of the first and second branch portions 22 and 23, first, asshown in FIG. 14A, the corresponding upper side wiring patterns 204 aextend from the neighborhood of the tail end portions of the secondbranch portions 23 by way of the first and second branch portions 22 and23 up to the via holes 206 in the neighborhood of the first branchportions 22 on the main line 21. And as shown in FIG. 14B, from the viaholes 206, the corresponding lower side wiring patterns 204 b extend upto the via holes 206 (see FIG. 16B) in the neighborhood of the connector212 on the main line 21. Further, as shown in FIG. 16A, from the viaholes 206, the corresponding upper side wiring patterns 204 a extend upto the connector 212, whereby the first and second branch portions 22and 23 and the connector 212 are connected so as to be electricalcontinuous. That is, at the portion of connection with the connector 212on the main line 21, the upper side wiring patterns 204 a correspondingto all the first and second branch portions 22 and 23 provided on bothsides in the width direction are connected to the connector 212 (seeFIG. 16B), and no lower side wiring patterns 204 b connected to theconnector 212 are present (see FIG. 16B).

By bringing the upper side wiring patterns 204 a and the lower sidewiring patterns 204 b together to the connector 212 by using both theupper side metal layer 203 a and the lower side metal layer 203 b asdescribed above, a plurality of wirings extending from a plurality ofbus bars 25 can be connected to the connector 212 while being rearrangedin the order corresponding to the order of arrangement of the singlecells 2 (see FIG. 2). That is, the wiring patterns can be arranged inthe order of potentials.

As shown in FIGS. 14A, 14B, 16A and 16B, the upper side dummy patterns205 a and the lower side dummy patterns 205 b are formed, mainly, in thenearly entire area except the area occupied by the upper side wiringpatterns 204 a and the lower side wiring patterns 204 b in the part ofthe main line 21 accommodated in the holder 30 (that is, the part exceptthe exposed part 213). The upper side dummy patterns 205 a and the upperside wiring patterns 204 a, and the lower side dummy patterns 205 b andthe lower side wiring patterns 204 b are disposed away from each otherso as not to be electrically continuous. These upper side dummy patterns205 a and lower side dummy patterns 205 b are provided mainly in orderthat the stiffness of the part of the main line 21 accommodated in theholder 30 (that is, the part except the exposed part 213) is higher thanthat of the first and second branch portions 22 and 23.

Further, as shown in FIG. 16B, the lower side dummy patterns 205 b(hereinafter, referred to particularly as “connector connection portiondummy patterns 207”) are formed in a predetermined area in the lengthdirection and substantially over the entire area in the width directionat the portion of connection between the main line 21 and the connector212. In other words, the connector connection portion dummy patterns 207are provided so as to be multilayered with respect to the upper sidewiring patterns 204 a connected to the connector 212.

Since a multiplicity of upper side wiring patterns 204 a are denselyconnected to the connector 212 as described above, the points of contactbetween the terminals incorporated in the connector 212 and the upperside wiring patterns 204 a are also dense. For this reason, the heatcaused by the contact resistance at each point of contact concentratesin a small space in the connector 212. It is desirable to release thisheat to the outside of the connector 212. In this regard, since theconnector connection portion dummy patterns 207 made of a metal are highin thermal conductivity, the heat inside the connector 212 can bereleased to the outside through the connector connection portion dummypatterns 207. Therefore, by providing the connector connection portiondummy patterns 207, the performance of heat release from the connector212 can be made higher than in a mode where no connector connectionportion dummy patterns 207 are provided. In addition, since thestiffness of the main line 21 at the portion of connection with theconnector 212 can be made higher by providing the connector connectionportion dummy patterns 207 than in the mode where no connectorconnection portion dummy patterns 207 are provided, for example,separation of the point of contact between the terminals and the upperside wiring patterns 204 a due to curving of the main line 21 can besuppressed.

In the example shown in FIG. 16B, an edge portion 207 a on the rear side(the side opposite to the side connected to the connector 212) on theconnector connection portion dummy pattern 207 is linear in shape. Thismakes the manufacture of the connector connection portion dummy patterns207 comparatively easy. On the contrary, as shown in FIG. 17, the edgeportion 207 a may be corrugated in shape. With this, the occurrence ofstress concentration inside the connector connection portion dummypatterns 207 when the main line 21 of the circuit body 20 is curved canbe avoided as much as possible.

Next, as shown in FIG. 14A, the connection portion 24 is formed on thetail end portion of each of the second branch portions 23 on all thefirst and second branch portions 22 and 23 provided on both sides of themain line 21 in the width direction. As shown in FIG. 15, the connectionportion 24 is disposed so as to be separate from a tail end portion 26of the upper side wiring pattern 204 a on the second branch portion 23.As described later, the bus bar 25 is connected to the connectionportion 24 and a chip fuse 50 is disposed so as to bridge between thetail end portion 26 and the connection portion 24 (see FIG. 10, etc.),whereby the bus bar 25 and the connector 212 are connected so as to beelectrically continuous.

As shown in FIG. 15, a thin portion 27 where the width (that is, thecross-sectional area) of the wiring pattern is relatively small isformed on the upper side wiring pattern 204 a on the second branchportion 23. Thereby, even if excessive current flows at a specificwiring pattern for various reasons and the chip fuse 50 does notfunction, the thin portion 27 corresponding to the wiring pattern meltsmore preferentially than the remaining part of the upper side wiringpattern 204 a because of the Joule heat caused by the excessive current.Thus, the remaining part of the upper side wiring pattern 204 a(particularly, the part where the upper side wiring patterns 204 a aredense on the main line 21) melts, so that adverse effects on theperipheral wirings and the like can be suppressed. Since the molten thinportion 27 is trapped in the resin layer 201, scattering around of themetal forming the thin portion 27 can be suppressed.

(Concrete Form of Connection Between the Connection Piece of the Bus Barand the Connection Portion of the Branch Line)

Next, referring to FIGS. 10, 11A and 11B, a concrete form of connectionbetween the connection piece 252 of the bus bar 25 and the connectionportion 24 of the second branch portion 23 will be described.

As shown in FIGS. 10, 11A and 11B, in the area, corresponding to theconnection portion 24 and the tail end portion 26, on the upper surfaceof the leading end portion 232 of the second branch portion 23, theresin layer 201 (see FIG. 11B) constituting the circuit body 20 isremoved. As a result, on the upper surface of the leading end portion232, the substantially U-shaped connection portion 24 and therectangular tail end portion 26 are exposed so as to be open at the top.

The connection piece 252 of the bus bar 25 is formed of a first portion252 a extending from the bus bar body 251 toward the inside in the widthdirection (the side of the main line 21) and a pair of second portions252 b and 252 c extending rearward from the leading end portion and thebase portion of the first portion 252 a. As a result, the connectionpiece 252 has a substantial U shape that is open to the rearcorresponding to the shape of the exposed connection portion 24.

The connection piece 252 (which has the first portion 252 a and thesecond portions 252 b and 252 c) is fixed to the upper surface of theexposed connection portion 24 over the entire area so that thesubstantial U shapes thereof coincide with each other. In this example,such fixing is made by using solder H. As a result, the connectionportion 24 and the bus bar 25 are connected so as to be electricallycontinuous, and by using the stiffness of the connection piece 252, anarea (curving restricted area) R where the curving of the second branchportion 23 is restricted is formed in a rectangular part sandwiched bythe pair of second portions 252 b and 252 c.

In this curving restricted area R, the chip fuse 50 is attached so as tobridge between the tail end portion 26 and the connection portion 24.Specifically, one of the electrodes on both end portions of the chipfuse 50 is fixed to the exposed connection portion 24, and the otherthereof is fixed to the exposed tail end portion 26. In this example,such fixing is made by using solder H. As a result, the connectionportion 24 (consequently, the bus bar 25) and the tail end portion 26(consequently, the connector 212) are connected so as to be electricallycontinuous.

As described above, the curving restricted area R is formed by theconnection piece 252 of the bus bar 25, and the chip fuse 50 is mountedin this area. Thereby, curving of the second branch portion 23 in themounting area of the chip fuse 50 can be suppressed without theprovision of a reinforcing plate or the like.

As shown in FIG. 12A, the connection piece 252 may have an L shape wherethe second portion 252 c is omitted from the mode shown in FIG. 11A.Moreover, as shown in FIG. 12B, the connection piece 252 may have arectangular shape where a third portion 252 d coupling the leading endsof the pair of second portions 252 b and 252 c is further provided inthe mode shown in FIG. 11A. Further, as shown in FIG. 12C, theconnection piece 252 may be formed of two first portions 252 a and 252 efrom the bus bar body 251. In any of the modes, since the chip fuse 50is attached within the curving restricted area R using the stiffness ofthe connection piece 252, curving of the second branch portion 23 in themounting area of the chip fuse 50 can be suppressed.

Further, as shown in FIGS. 13A and 13B, a potting member 28 may beprovided so as to cover the chip fuse 50 so that it is separated fromthe outside in the curving restricted area R formed by the connectionpiece 252 by using the structure such that the height of the connectionpiece 252 (which has the first portion 252 a and the second portions 252b and 252 c) is larger than the height of the chip fuse 50 (see FIG.11B).

As described above, by the potting member 28 covering the chip fuse 50,the waterproofing property of the chip fuse 50 and the electric contactsaround the chip fuse 50 can be enhanced. Further, by the potting member28 solidifying in a state of being in intimate contact with the surfaceof the leading end portion 232, curving of the second branch portion 23can be further suppressed by using the stiffness of the potting member28. It is desirable that the potting member 28 be provided so as to fillthe entire curving restricted area R formed by the connection piece 252of the bus bar 25.

(Cover Assembled to the Holder)

Next, referring to FIGS. 18A and 18B to 21A to 21C, a cover 40 assembledto the holder 30 will be described. As shown in FIGS. 18A and 18B, thecover 40 made of resin is assembled to the holder 30 accommodating thecircuit body 20 from above so as to cover the circuit body 20 in orderto protect the circuit body 20. Under the condition where the cover 40is assembled to the holder 30, the exposed part 213 of the circuit body20 is exposed to the outside from the space covered with the holder 30and the cover 40 (see FIG. 18B).

As described above, the holder 30 is stretchable and shrinkable in thefront-rear direction (the assembled direction of the battery assembly1). For this reason, it is desirable that the cover 40 be alsoconfigured so as to be stretchable and shrinkable in the front-reardirection. In this regard, the cover 40 is formed of two portionsarranged in the front-rear direction (that is, a front side portion 41and a rear side portion 42), and the front side portion 41 and the rearside portion 42 are coupled so as to be movable relatively to each otherin the front-rear direction. Hereinafter, concrete structures of thefront side portion 41 and the rear side portion 42 will be described.

As shown in FIGS. 20A and 20B, the front side portion 41 issubstantially formed of a rectangular plate form top plate portion 411and a pair of side plate portions 412 hanging down from both sides ofthe top plate portion 411 in the width direction. The rear side portion42 is also substantially formed of a rectangular plate form top plateportion 421 and a pair of side plate portions 422 hanging from bothsides of the top plate portion 421 in the width direction.

As shown in FIG. 19, the side plate portions 412 of the front sideportion 41 and the side plate portions 422 of the rear side portion 42are provided with a plurality of engagement portions 43 so as tocorrespond to engagement portions 37 provided in a plurality ofpositions in the front-rear direction on both side walls of the holder30 (see FIGS. 1 and 6). The corresponding engagement portions 37 of theholder 30 and engagement portions 43 of the cover 40 engage with eachother, whereby the cover 40 (=the front side portion 41 and the rearside portion 42) is assembled to the holder 30.

As shown in FIGS. 20A and 20B, on the top plate portion 411 of the frontside portion 41, an engagement hole (through hole) 413 is formed in acentral portion in the width direction in the neighborhood of the rearend portion (the portion to be coupled to the rear side portion 42).Moreover, on the rear end portion of the top plate portion 411, a firstcoupling plate portion 414 is formed in a position slightly lower thanthe top plate portion 411 in a central portion in the width direction,and on both sides of the first coupling plate portion 414 in the widthdirection, a pair of second coupling plate portions 415 that are flushwith the top plate portion 411 are formed.

On the top plate portion 421 of the rear side portion 42, atongue-shaped piece 423 is formed that projects forward from a centralportion of the front end portion (the portion to be coupled to the frontside portion 41) in the width direction. On a central portion of theupper surface of the tongue-shaped piece 423, a projection 423 aprojecting upward is formed. Moreover, on the front end portion of thetop plate portion 421, a first coupling plate portion 424 that is flushwith the top plate portion 421 is formed in a central portion in thewidth direction, and on both sides of the first coupling plate portion424 in the width direction, a pair of second coupling plate portions 425are formed in positions slightly lower than the top plate portion 421.

Under a condition where the front side portion 41 and the rear sideportion 42 are coupled together, as shown in FIGS. 20A and 21A, thetongue-shaped piece 423 of the rear side portion 42 enters the verticalgap between the top plate portion 411 and the first coupling plateportion 414 of the front side portion 41, and the projection 423 a ofthe tongue-shaped piece 423 is situated inside the engagement hole 413.Moreover, the first coupling plate portion 414 enters below the firstcoupling plate portion 424 and the pair of second coupling plateportions 415 enters above the pair of second coupling plate portions425, whereby the first coupling plate portion 414 and the first couplingplate portion 424 partially overlap with each other, and the pair ofsecond coupling plate portions 415 and the pair of second coupling plateportions 425 partially overlap with each other.

Under a condition where the front side portion 41 and the rear sideportion 42 are coupled together, the front side portion 41 and the rearside portion 42 are stretchable in the front-rear direction until theprojection 423 a abuts on the rear side end of the engagement hole 413as shown in FIG. 21B, and are shrinkable in the front-rear directionuntil a leading end portion 423 b of the tongue-shaped piece 423 abutson a stopper wall 417 provided on the lower surface of the top plateportion 411 of the front side portion 41 as shown in FIG. 21C.

Thus, the cover 40 formed of the front side portion 41 and the rear sideportion 42 coupled together is configured so as to be stretchable andshrinkable. As a consequence, the cover 40 also stretches and shrinks asthe holder 30 stretches and shrinks, so that the circuit body 20 and thebus bars 25 can be protected from the outside while the assemblabilityto the battery assembly 1 and the conformability to the manufacturingvariations are improved.

Further, in whichever position in the stretchable and shrinkable rangethe front side portion 41 and the rear side portion 42 are situated, thefirst coupling plate portion 414 and the first coupling plate portion424 partially overlap with each other, and the pair of second couplingplate portions 415 and the pair of second coupling plate portions 425partially overlap with each other. That is, in whichever position in thestretchable and shrinkable range the front side portion 41 and the rearside portion 42 are situated, the portion of coupling of the front sideportion 41 and the rear side portion 42 is closed so that the inside andoutside of the cover 40 do not communicate with each other. As aconsequence, even if the cover 40 stretches or shrinks, the conditionwhere the circuit body 20 and the bus bars 25 are protected from theoutside can be maintained.

Further, since the cover 40 is configured so as to be stretchable andshrinkable, the degree of absorbing the manufacturing variations and thelike at the engagement portions 37 of the holder 30 and the engagementportions 43 of the cover 40 can be made lower than that in a mode wherethe cover 40 cannot stretch or shrink. As a result, the engagementportions 37 of the holder 30 and the engagement portions 43 of the cover40 can be made small.

(Protector Fixed to the Cover)

Next, referring to FIGS. 22 to 24A and 24B, a protector 70 fixed to thecover 40 will be described. The protector 70 made of resin is providedon the exposed part 213 of the circuit body 20 in order to protect theexposed part 213 of the circuit body 20.

As shown in FIGS. 23A and 23B, the protector 70 is formed of a base endside accommodation portion 71, a leading end side accommodation portion72 and a coupling portion 73. The base end side accommodation portion 71has a rectangular plate shape. Using engagement portions 71 a on bothsides in the width direction, the base end side accommodation portion 71is assembled from above to be fixed to a front end portion 38 of theholder 30 accommodating the circuit body 20, so as to cover the baseportion of the exposed part 213 of the circuit body 20. Thereby, thebase portion of the exposed part 213 of the circuit body 20 isaccommodated so as to be slidable in the length direction by the baseend side accommodation portion 71 and the front end portion 38 of theholder 30.

The leading end side accommodation portion 72 is formed of a rectangularplate form upper side portion 72 a and lower side portion 72 b. Theupper side portion 72 a and the lower side portion 72 b are assembled toeach other so as to sandwich a central portion of the exposed part 213of the circuit body 20 in the length direction by the upper side portion72 a and the lower side portion 72 b by using engagement portions 72 con both sides in the width direction. Thereby, the central portion ofthe exposed part 213 of the circuit body 20 is accommodated so as to beslidable in the length direction by the leading end side accommodationportion 72 formed of the upper side portion 72 a and the lower sideportion 72 b.

The coupling portion 73 is formed of a plurality of (in this example,three) bendable belts that couple the base end side accommodationportion 71 and the upper side portion 72 a of the leading end sideaccommodation portion 72.

As shown in FIG. 22, the connector 212 situated at the leading end ofthe exposed part 213 is connected to a connector connection portion 61of the voltage detector 60 disposed on the upper surface of the cover 40under a condition where the exposed part 213 of the circuit body 20 isfolded back from the base portion thereof toward the upper surface ofthe cover 40. Under this condition, the coupling portion 73 of theprotector 70 is curved, and the leading end side accommodation portion72 is fixed to the upper surface of the cover 40 by engaging engagementportions 72 d on both sides thereof in the width direction (see alsoFIGS. 23A and 23B) with engagement portions 416 of the cover 40 (seealso FIGS. 20A and 20B, etc.).

As shown in FIGS. 24A and 24B, by sliding the circuit body 20 withrespect to the leading end side accommodation portion 72, the circuitbody 20 can be deformed in a direction away from the coupling portion 73also under a condition where the coupling portion 73 is curved and theleading end side accommodation portion 72 is fixed to the upper surfaceof the cover 40. That is, the deformation of the circuit body 20 is notprevented. For this reason, not only the connector 212 is movable in thefront-rear direction relatively to the cover 40 but also handling of thecircuit body 20 can be made easy.

(Main Effects of the Present Embodiment)

According to the bus bar module 10 according to the present embodiment,the circuit body 20 formed of a flexible board has the main line 21 thatcan be disposed on the upper part of the single cells 2, the firstbranch portions 22 extending outward from the side portions of the mainline 21, and the second branch portions 23 connecting with the firstbranch portions 22 and extending parallel to the assembled direction ofthe single cells 2. The second branch portion 23 is provided with thefolded portion 231 folded around the axis L intersecting in theassembled direction (in the width direction). For this reason, when thesingle cells 2 repetitively stretch and shrink in the thicknessdirection (assembled direction) and when the positions of the singlecells 2 differ among the manufactured battery assemblies 1 due to theassembly tolerances of the single cells 2, the folded portions 231 ofthe second branch portions 23 bend and stretch, so that the bus bars 25are movable in the thickness direction of the single cells 2.

As described above, the bus bar module 10 is capable of easily handlingthe stretch and shrinkage and the manufacturing variations of thebattery assembly 1 substantially by the deformation of only the firstand second branch lines 22 and 23 without the need for any deformationof the main line 21 of the circuit body 20. Moreover, even when amultiplicity of circuit structures are contained, the flexible board istypically easy to become deformed flexibly with a far smaller force thannormal electric wires used for the above-described conventional bus barmodule. For this reason, the assemblability to the battery assembly 1 issignificantly improved. Therefore, the bus bar module 10 is excellent inthe assemblability to the battery assembly 1 and the conformability tothe deformation and the manufacturing variations of the battery assembly1.

Further, in the bus bar module 10 according to the present embodiment,the folded portions 231 are provided in such a manner that the lowersurfaces of the connection portions 24 of the second branch portions 23are along a surface different from the lower surface of the main line21. Therefore, contact between the single cells 2 and the main line 21can be suppressed without the provision of a projecting plate or thelike on the upper surfaces of the single cells 2. Therefore,contribution can be made to reduction in height, reduction in the numberof parts, simplification of the manufacturing process and the like ofthe bus bar module 10.

Further, in the bus bar module 10 according to the present embodiment,the second branch portions 23 are formed in an S shape provided with thefirst folded portion 231A and the second folded portion 231B. For thisreason, even if the relative positions of the bus bars 25 change in anydirection in the length direction of the main line 21, the change can befollowed, and return to the initial position is made possible.

Further, in the bus bar module 10 according to the present embodiment,since the cover 40 also stretches and shrinks in the laminationdirection as the holder 30 stretches and shrinks in the laminationdirection, the circuit body 20 and the bus bar 25 can be protected fromthe outside while the assemblability to the battery assembly 1 and theconformability to the manufacturing variations are improved.

Further, in the bus bar module 10 according to the present embodiment,irrespective of in which positions in the stretchable and shrinkablerange the front side portion 41 and the rear side portion 42constituting the cover 40 are situated, the portion of coupling of thefront side portion 41 and the rear side portion 42 are closed so thatthe inside and outside of the cover 40 do not communicate with eachother. Consequently, even if the cover 40 stretches and shrinks, thecondition where the circuit body 20 and the bus bar 25 are protectedfrom the outside can be maintained.

The present invention is not limited to the above-described embodiments,and various modifications may be adopted within the scope of the presentinvention. For example, the present invention is not limited to theabove-described embodiment, and modifications, improvements and the likeare possible as appropriate. Besides, the materials, shapes, dimensions,numbers, disposition positions and the like of the elements of theabove-described embodiment are arbitrary as long as the presentinvention is attained, and are not limited.

Now, features of the above-described embodiment of the bus bar module 10according to the present invention is briefly summarized and listed inthe following [1] to [3]:

[1] There is a provided a bus bar module (10) configured to be attachedto a battery assembly (1) having a plurality of single cells (2) whichare assembled to each other along a first direction, the bus bar module(10) including:

a circuit body (20) configured by a flexible board on which a wiringpattern (204 a, 204 b) is provided;

a bus bar (25) configured to be connected to an electrode of each of thesingle cells;

a holder (30) configured to hold the bus bar (25) and being stretchableand shrinkable in the first direction; and

a cover (40) configured to be assembled to the holder (30) to protectthe circuit body (20) and the holder (30),

wherein the circuit body (20) includes:

-   -   a belt-like main line (20) that extends in the first direction;    -   a belt-like branch line (22, 23) that extends from the main line        (20) so as to branch from the main line (20), a part of the        branch line (23) extending in the first direction and including        a folded portion (231) having a shape folded back around an axis        (L1, L2) intersecting with the first direction; and    -   a connection portion (24) provided in a position closer to a        distal end of the branch line than the folded portion and        configured to be connected to the bus bar; and

wherein the cover (40) is structured so as to be stretchable andshrinkable in the first direction in accordance with a stretching and ashrinking of the holder (30) in the first direction.

[2] In the bus bar module according to the above [1], the cover (40) hasa plurality of portions (41, 42) arranged in the first direction and theplurality of portions are coupled to each other so as to be movablerelatively to each other.[3] In the bus bar module according to the above [2], a movable range ofeach of the plurality of portions is limited, and each of the pluralityof portions is structured so as to prevent an inside and outside of thecover from communicating with each other even when each of the pluralityof portions is arranged in the movable range.

What is claimed is:
 1. A bus bar module configured to be attached to abattery assembly having a plurality of single cells which are assembledto each other along a first direction, the bus bar module comprising: acircuit body configured by a flexible board on which a wiring pattern isprovided; a bus bar configured to be connected to an electrode of eachof the single cells; a holder configured to hold the bus bar and beingstretchable and shrinkable in the first direction; and a coverconfigured to be assembled to the holder to protect the circuit body andthe holder, wherein the cover is structured so as to be stretchable andshrinkable in the first direction in accordance with a stretching and ashrinking of the holder in the first direction.
 2. The bus bar moduleaccording to claim 1, wherein the cover has a plurality of portionsarranged in the first direction and the plurality of portions arecoupled to each other so as to be movable relatively to each other. 3.The bus bar module according to claim 2, wherein a movable range of eachof the plurality of portions is limited, and each of the plurality ofportions is structured so as to prevent an inside and outside of thecover from communicating with each other even when each of the pluralityof portions is arranged in the movable range.